Enhancement of luminescence of Rhodamine B by gold nanoparticles in thin films on glass for active optical materials applications

Fluorescent dyes in solid matrices have many potential applications provided that their high optical efficiencies are achieved. We present here gold nanoparticles formed and incorporated together with fluorescent dye Rhodamine B into a film of polyvinyl alcohol (PVA). The increase of fluorescence of the dye results from its interaction with surface plasmons. The electric charge on the gold nanoparticles and the distance between them and the dye molecules has a significant effect on the fluorescence intensity. Fluorescence enhancement of 74% was achieved for the negatively charged particles. Dynamic measurements reveal decrease of fluorescent lifetimes of the dye in presence of gold nanoparticles. Our findings enable utilization of films with enhanced fluorescence in optical materials such as luminescence solar concentrators, solid state tunable laser and active waveguides.     

Maturing,Technology-Based,Born-Global Companies: Surviving Through Mergers and Acquisitions

To date, there has been little research about the corporate growth of born-global companies and relatively little data exist about their maturation, survival as independent companies (or failure to do so) and their international strategies. The present paper is based on an empirical study of Israeli technology-based companies that were identified in the late 1990s as born global. We collected data about the continuing development of these firms for the decade spanning 2000–2009. Our findings show that maturing technology-based, born-global companies can increase their chances of survival by acquiring other firms. Although such acquisitions do not increase profits, they allow born-global firms to continue increasing their sales and to expand and upgrade their product line, which in turn increases their chances of remaining independent. The data also show that if the firms prefer to merge with another company, they are in a better position if they do not acquire any other firms beforehand. Finally, our data show that although the majority of born-global companies can continue operations if they survived the first decade, they are not highly successful on the measures of growth and shareholder wealth. One of the recommendations of this study is that for maturing, technology-based, born-global companies to remain successful, they must be more aggressive in their M&A strategy than they are at the moment.     

Self-stabilization of dynamic systems assuming only read/write atomicity

Summary Three self-stabilizing protocols for distributed systems in the shared memory model are presented. The first protocol is a mutual-exclusion prootocol for tree structured systems. The second protocol is a spanning tree protocol for systems with any connected communication graph. The thrid protocol is obtianed by use offair protoco combination, a simple technique which enables the combination of two self-stabilizing dynamic protocols. The result protocol is a self-stabilizing, mutualexclusion protocol for dynamic systems with a general (connected) communication graph. The presented protocols improve upon previous protocols in two ways: First, it is assumed that the only atomic operations are either read or write to the shared memory. Second, our protocols work for any connected network and even for dynamic network, in which the topology of the network may change during the excution. Shlomi Dolev received his B.Sc. in Civil Engineering and B.A. in Computer Science in 1984 and 1985, and his M.Sc. and Ph.D. in computer Sciene in 1989 and 1992 from the Technion Israel Institute of Technology. He is currently a post-dotoral fellow in the Department of Computer Science at Texas A & M Univeristy. His current research interests include the theoretical aspects of distributed computing and communcation networks. Amos Israeli received his B.Sc. in Mathematics and Physics from Hebrew University in 1976, and his M.Sc. and D.Sc. in Computer Science from the Weizmann Institute in 1980 and the Technion in 1985, respectively. Currently he is a sensior lecturer at the Electrical Engineering Department at the Technion. Prior tot his he was a postdoctoral fellow at the Aiken Computation Laboratory at harvard. His research interests are in Parellel and Distributed Computing and in Robotics. In particular he has worked on the design and analysis of Wait-Free and Self-Stabilizing distributed protocols. Shlomo Moran received his B.Sc. and D.Sc. degrees in matheamtics from Technion, Israel Institute of Technology, Haifa, in 1975 and 1979, respectively. From 1979 to 1981 he was assistant professors and a visiting research specialist at the University of Minnesota, Minneapolis. From 1981 to 1985 he was a senior lecturer at the Department of Computer Science. Technion, and from 1985 to 1986 he visted at IBM Thoas J. Watson Research Center, Yorktown Heights. From 1986 to 1993 he was an associated professor at the Department of Computer Science, Technin. in 1992–3 he visited at AT & T Bell Labs at Murray Hill and at Centrum voor Wiskunde en Informatica, Amsterdam. From 1993 he is a full professor at the Department of Computer Science, Technion. His researchinterests include distributed algorithm, computational complexity, combinatorics and grapth theory.Part of this research was supported in part by Technion V.P.R. Funds — Wellner Research Fund, and by the Foundation for Research in Electronics, Computers and Communictions, administrated by the Israel Academy of Sciences and Humanities.     

The Impact of Breaks on Forgetting When Performing A Repetitive Task

Commonly used learning curve models assume that a repetitive task is performed continuously, disregarding the existence of possible break periods between consecutive repetitions. Since these breaks generate forgetting, actual performance will be inferior to the performance forecasted by typical learning curve models.

This paper describes and analyzes a laboratory experiment designed to investigate the nature of forgetting in a working environment. The results of the experiment indicate that the degree of forgetting is a function of the break length and the level of experience gained prior to the break. The study investigated the impact of breaks within a range of one to eighty two days. The performance deterioration due to the breaks was just a few percentage points for a single day break and up to 70 percentage points for the longest breaks. A power curve was identified as a proper forgetting model to depict the relationship between break length, performance time before the break and the degree of forgetting.     

Resource-bounded sensing and planning in autonomous systems

This paper is concerned with the implications of limited computational resources and uncertainty on the design of autonomous systems. To address this problem, we redefine the principal role of sensor interpretation and planning processes. Following Agre and Chapman's plan-as-communication approach, sensing and planning are treated as computational processes that provide information to an execution architecture and thus improve the overall performance of the system. We argue that autonomous systems must be able to trade off the quality of this information with the computational resources required to produce it. Anytime algorithms, whose quality of results improves gradually as computation time increases, provide useful performance components for time-critical sensing and planning in robotic systems. In our earlier work, we introduced a compilation scheme for optimal composition of anytime algorithms. This paper demonstrates the applicability of the compilation technique to the construction of autonomous systems. The result is a flexible approach to construct systems that can operate robustly in real-time by exploiting the tradeoff between time and quality in planning, sensing and plan execution.     

Fluridone adsorption–desorption on organo-clays

The adsorption–desorption of the herbicide fluridone on Na-montmorillonite and several organo-montmorillonite complexes was studied at a variety of loadings of the organic cation and pH levels. The aim was to find the organo-clay complex, which would be an optimal adsorbent for the hydrophobic fluridone. The organic cations studied were hexadecyltrimethylammonium (HDTMA), benzyltriethylammonium (BTEA), benzyltrimethylammonium (BTMA) and methylene blue (MB) at loadings equal to 25%, 50% and 100% of the cation exchange capacity (CEC) of the clay-mineral. The adsorbed amount of fluridone increased several-fold when montmorillonite was preadsorbed by the organic cation HDTMA up to its CEC and with BTMA at a loading of 5/8 of the CEC. BTEA and MB did not improve the adsorption capacity of the clay for fluridone. The results suggest that interactions between the phenyl rings of the herbicide and that of a small organic cation are geometrically easier to establish than with a larger organic cation. A reduced interaction between the phenyl rings of MB and those of fluridone may account for the low affinity of fluridone adsorption on montmorillonite-MB. In all cases, fluridone adsorption increased with decreasing pH and reached 100% for pH 2.7. Protonation of fluridone molecules with decreasing pH would result in increased adsorption through cation exchange. Thus, by regulating the pH, complete fluridone adsorption can be achieved. Desorption isotherms demonstrate high degree of irreversibility of the adsorption–desorption process and suggest that strong binding mechanisms dominate the fluridone-clay and organo-clay interactions. The results for fluridone adsorption–desorption demonstrate that, for similar molecules, a clay-based slow release formulation can be designed by first lowering the pH.     

Performance of linear MMSE multiuser detection combined with a standard IS-95 uplink

Current implementation of IS-95 based systems is performance limited due to the use of a “conventional” detection scheme, which is susceptive to inter-user interference. We focus on the uplink, and try to examine the performance enhancement achieved by a suboptimal linear multiuser MMSE pre-filter, applied in front of the “standard” detection mechanism. We demonstrate the limitations of this relatively simple approach, and the constellations in which it may show improved performance. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the complexity of simple arithmetic expressions

Let $\text{E}$ be the set of all simple arithmetic expressions of the form E(x) = xT_l…T_k where x is a nonnegative integer variable and each T_i is a multiplication or integer division by a positive integer constant. We investigate the complexity of the inequivalence and the bounded inequivalence problems for expressions in $\text{E}$. (The bounded inequivalence problem is the problem of deciding for arbitrary expressions E₁(x) and E₂(x) and a positive integer l whether or not E₁(x) ≠ E₂(x) for some nonnegative integer x<l. If l = ∞, i.e., there is no upper bound on x, the problem becomes the inequivalence problem.) We show that the inequivalence problem (or equivalently, the equivalence problem) for a large subclass of $\text{E}$ is decidable in polynomial time. Whether or not the problem is decidable in polynomial time for the full class $\text{E}$ remains open. We also show that the bounded inequivalence problem is NP-complete even if the divisors are restricted to be equal to 2. This last result can be used to sharpen some known NP-completeness results in the literature. Note that if division is rational division, all problems are trivially decidable in polynomial time.